<template>
  <div class="todo-footer" v-show="total">
          <label>
            <input type="checkbox" v-model="isAll"/>
          </label>
          <span>
            <span>已完成{{doneTodos}}</span> / 全部{{total}}
          </span>
          <button class="btn btn-danger"
          @click="clearAll"
          >清除已完成任务</button>
   </div>
</template>

<script>
export default {
    name:'MyFooter',
    props:['todos','itemCheckeAll','itemClearAll'],
    methods: {
      clearAll(){
        this.itemClearAll()
      }
    },
    computed:{
      total(){
        return this.todos.length
      },
      doneTodos(){
        return this.todos.reduce((pre,cur)=>pre+(cur.completed?1:0),0)
      },
      isAll:{
        // value返回的是当前选择框的是否勾选，他的状态将会直接影响列表里的所有值
        get(){
          return this.doneTodos === this.total 
          && this.total>0
        },
        set(value){
          this.itemCheckeAll(value)
        }
      }
    }
}
</script>

<style scoped>
    /*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>